Is Facebook developing its own smartphone? That’s a question that was on our radar back in September when Mike Arrington from TechCrunch speculated on the existence of such a device. Then, later, Facebook came out to deny that it was working on a handset and instead developing ways to better integrate its service into existing hardware.

It looks like we’ll know for sure what Facebook has planned on November 3 after their “mobile event” at its HQ. There are a lot of possibilities here.

Hardware

Facebook could indeed be working on a Facebook phone, but probably not one with a proprietary operating system. Our best guess is that a Facebook phone would come on special hardware (probably with a keyboard, made by Motorola or HTC) running on a heavily modified version of Android, perhaps with Gingerbread underpinnings. Perhaps they’ll utilize a side-sliding keyboard, or the less common candybar QWERTY design (BlackBerry/Moto Droid Pro style).

Deeper Integration

Facebook could have found a way to more deeply integrate its features into Android. Perhaps the native messaging application will tap the Facebook messaging system, the photo gallery will synchronize from your Facebook albums, and so on.

Widgets

It’s easy to see how Facebook could come up with a wide variety of custom widgets for Android: one that feeds your wall messages, one that tells you if you have a new Facebook instant message, one that informs you of birthdays, one that suggests new friends, and so on.

Other Possibilities

But perhaps there will be no Facebook phone. Perhaps Facebook will announce that its services will be tightly integrated into the next version of Android. Or, less realistically, Facebook could launch a cellular carrier (MVNO). If you’re making a call to a Facebook friend, the call will be routed over VoIP and won’t be counted against your minutes.

In the end, Facebook is going to announce some new mobile experience that will be far more immersive than the ubiquitous mobile Facebook app alone. Who is going to want a Facebook phone? I’m sure you or someone you know spend many hours per week on Facebook. They’d probably enjoy a richer experience from their mobile phone. Or, at least, that’s what Facebook is thinking.